1. Field of the Invention
The invention relates to a catheter that can be used for dialysis or for other procedures where the catheter is implanted for an extended period of time.
2. Description of the Related Art
Dialysis and some chemotherapy regimens require a catheter to be implanted in a patient for an extended time (e.g., several weeks, several months or longer). Catheters for dialysis extend from an externally accessible location on the patient (typically on the chest) to a location where there is a high flow of blood (typically near the heart). The high blood flow enables a sufficient volume of blood to be processed through the catheter and cleaned by the dialysis machine. Catheters used for chemotherapy and other drug administration purposes are extended from an externally accessible location on the patient to a location where the drug is likely to be most effective. The following discussion will pertain mostly to catheters intended for dialysis. However, the subject invention is applicable to all catheters that are implanted for an extended time.
A discussion of catheters is provided in Venous Catheters A Practical Manual by Pieters et al. Chapter 4 of that work is entitled Central Venous Catheters: Materials, Designs and Selection by Matthew A. Mauro, and the disclosure of that Chapter 4 is incorporated herein by reference.
Briefly, the distal end of a dialysis catheter should be placed close to the heart for optimum exchange of blood. Doctors typically want to know the location of the distal end of the dialysis catheter with considerable precision. The proximal end of the dialysis catheter desirably is at a location that can be accessed conveniently during dialysis and that is unobtrusive between the periodic dialysis procedures. Many doctors choose to direct the dialysis catheter through the jugular vein. However, the neck certainly is not the unobtrusive location for keeping the proximal end of the dialysis catheter between the periodic dialysis procedures.
The dialysis catheter typically is formed from a flexible material, such as silicone. A typical medical procedure for implanting a dialysis catheter involves first placing a small incision in the skin of the neck over the jugular vein. Subsequently, the jugular vein is cannulated. A peelable introducer sheath then is advanced an appropriate distance into the blood vessel so that the end of the catheter is at the precise position preferred by the doctor. The doctor then employs a tunnel dilator to create a subcutaneous tunnel that permits the proximal end of the catheter to be at a less obtrusive position. The subcutaneous tunnel typically extends slightly below the skin from a location on the chest and under the clavicle to a location where the catheter has been introduced into the jugular. The doctor directs the catheter through the tunnel, to the neck, through the incision in the neck and through the introducer sheath. The introducer sheath then is removed. A hub at the proximal end of the catheter may include a Luer fitting that enables the proximal end of the catheter to be placed in communication with the dialysis machine. Several closure means are provided on or near the proximal end of the catheter to prevent unintended blood loss between the periodic dialysis procedures.
Blood pressure and other forces within the body tend to urge the catheter from the body. Hence, proper anchoring is important. One common anchoring means provides a cuff extending around the portion of the catheter in the tunnel that extends from the upper chest to the neck of the patient. The cuff typically is formed from polyester. Scar tissue accumulates around the cuff and functions to hold the catheter in place. The scar tissue may also function as a barrier to bacterial infection. The scar tissue results in at least a semi-permanent anchoring of the catheter. In this regard, semi-permanent means that the catheter will remain in the patient until the cuffed portion of the catheter is dissected from the patient. This dissection can be complicated.
Dialysis catheters vary considerably from one manufacturer to another. However, a common requirement for virtually all dialysis catheters is an ability to locate the distal end of the catheter and the cuff with considerable precision. Accordingly, the doctor has limitations on the distance between the distal tip of the catheter and the cuff depending upon physical characteristics of the patient. A smaller patient will require a smaller tip-to-cuff distance, while a larger patient will require a larger tip-to-cuff distance. In view of these physical differences between patients, most dialysis catheter manufacturers provide catheters with different tip-to-cuff length. Accordingly, hospitals must maintain an appropriate inventory of different length dialysis catheters and the doctor must ensure that a catheter of appropriate length is available for implementation. There are costs and complications associated with a need to maintain an inventory of different products.
Compromises often must be made when a doctor selects a dialysis catheter from an inventory of catheters with different lengths. In this regard, dialysis catheters often come with tip-to-cuff lengths of 19 cm, 23 cm, 28 cm and 32 cm. A selection of a catheter of one of these lengths may require the doctor to move the tip or the cuff from its optimal position.
Arrow Cannon markets a dialysis catheter with most of the features described above. The Arrow Cannon catheter is promoted as having an ability to assure accurate tip placement. In this regard, the tip of the catheter is placed in the jugular in the manner described above. Proximal portions of the catheter then are urged in a retrograde direction through the tunnel from the neck to the selected location on the chest. The portion of the catheter emerging from the chest then is cut. A compression cap and compression sleeve are mounted separately to the cut proximal end of the catheter and a hub is threadedly engaged with the compression cap. The above-described Arrow Cannon catheter has the above-described problems associated with inventory management. Additionally, even though the tip may be positioned accurately, the cuff location is dependent upon the different tip-to-cuff dimensions in the inventory. Additionally, the retrograde movement of the catheter through the tunnel requires a technique that many doctors are not accustomed to. Furthermore, the intraoperative assembly of the compression sleeve with the compression cap requires more procedural steps and takes additional time.
U.S. Pat. No. 5,989,213 relates to a dialysis catheter with a guide tube that fits into the blood vessel. A tissue ingrowth member is secured to proximal portions of the guide catheter for affixation to the subcutaneous tissue. Thus, distal portions of the guide catheter of U.S. Pat. No. 5,989,213 reside in the blood vessel and proximal portions of the guide catheter are secured to the subcutaneous tissue. The dialysis catheter then is passed through the guide catheter. The distal end of the dialysis catheter is disposed at an appropriate location in the circulatory system, and distally of the distal end of the guide catheter. Proximal ends of the dialysis catheter are disposed externally on the patient, and proximally of the proximal end of the guide catheter. The system shown in U.S. Pat. No. 5,989,213 permits a desired distance between the distal tip of the catheter and the tissue ingrowth cuff. However, the system shown in U.S. Pat. No. 5,989,213 is not trimmable and hence requires an extensive inventory of catheters of different length to ensure that an excess of the catheter is not disposed externally of the patient.
Accordingly, it is an object of the subject invention to provide an improved catheter that can be implanted for an extended time, such as a dialysis catheter.
Another object of the subject invention is to provide a catheter that substantially avoids the need to maintain a significant inventory, while permitting precise positioning of both the tip and the cuff.
A further object of the invention is to provide a catheter that is convenient to implant and that ensures a precise exit site on the chest for the catheter.